Fixation of bone implants

ABSTRACT

An orthopedic screw includes a main body having a torqueing end, an inner chamber formed therein, and at least two mating features separated by a separation gap, the separation gap extending into the inner chamber, at least one of the at least two mating features having a first tapered portion with an increasing width and a second tapered portion with a decreasing width; and a support member removably placed in the inner chamber of the main body and having a support portion at least partially filling the separation gap between the at least two mating features.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 14/987,293,entitled “FIXATION OF BONE IMPLANTS”, filed Jan. 4, 2016, which isincorporated herein by reference. U.S. patent application Ser. No.14/987,293 is a continuation of U.S. patent application Ser. No.14/204,693, entitled “FIXATION OF BONE IMPLANTS”, filed Mar. 11, 2014,which is incorporated herein by reference. U.S. patent application Ser.No. 14/204,693 is a non-provisional application based upon U.S.provisional patent application Ser. No. 61/789,158, entitled “FIXATIONOF BONE IMPLANTS”, filed Mar. 15, 2013, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to orthopaedic implants, and, moreparticularly, to fixation screws for orthopaedic implants.

2. Description of the Related Art

The knee is a common site of orthopaedic problems in patients thatrequire surgery. The cartilage in the knee is especially vulnerable toinjury throughout a patient's lifetime and generally does not repairitself like other tissues in the body. When the cartilage in a knee isdamaged or destroyed, the femur and tibia, which are normally separatedand lubricated by the cartilage, can rub together, which causes variousproblems.

If surgical intervention to repair the cartilage of the knee isinsufficient, a knee implant is usually implanted into the patient on aprepared surface of either the femur or tibia. Knee implants typicallyhave an articulating surface that simulates the body's naturalcartilage, allowing the femur and tibia to stay connected and gliderelative to each other as they would if healthy cartilage was present.

When installing the knee implant, an adhesive is often used to affix theimplant to either the femur or tibia and allow for proper fixation ofthe implant. Bone cement is a popular adhesive choice because it forms agood interface with the bone and has good biocompatibility. There areseveral advantages that could be gained from reducing the use of bonecement to fixate a knee implant to the prepared bone surface. Bonecement has a putty-like consistency and is prone to spreading duringsurgery. When the surgeon presses the knee implant on to the bone cementon the prepared bone surface, there is a risk of bone cement squeezingout from between the knee implant and the prepared bone surface if anexcessive amount of bone cement or pressing force is applied. This loosebone cement is usually removed during surgery, which prolongs thesurgery.

One approach that has been used in place of bone cement is fixating theimplant using an orthopaedic screw. The orthopaedic screw is advancedinto bone tissue and abuts against the implant, fixating the implant tothe bone. One problem with known orthopaedic screws is that the screwsare susceptible to being loosened during implantation and canprematurely be removed from the implant. Another problem is that thetorqued end of the orthopaedic screw can become stripped duringimplantation due to the high torque forces applied to the screw toadvance the screw through bone tissue, making it difficult to remove thescrew after implantation.

What is needed in the art is a way to fixate implants to bone tissuethat overcomes some of the described disadvantages present in the art.

SUMMARY OF THE INVENTION

The present invention provides implant systems with an implant having abore with a lip and a screw that has mating features which can abutagainst the lip and be kept separated by a support member.

The invention in one form is directed to an orthopaedic screw includinga main body having a torqueing end, an inner chamber formed therein, andat least two mating features separated by a separation gap, theseparation gap extending into the inner chamber, at least one of the atleast two mating features having a first tapered portion with anincreasing width and a second tapered portion with a decreasing width;and a support member removably placed in the inner chamber of the mainbody and having a support portion at least partially filling theseparation gap between the at least two mating features.

The invention in another form is directed to an orthopaedic screwincluding a main body having a torqueing end, an inner chamber formedtherein, and at least two mating features separated by a separation gap,the separation gap extending into the inner chamber, at least one of theat least two mating features having a first tapered portion with anincreasing width and a second tapered portion with a decreasing width

An advantage of the present invention is that the orthopaedic screw canbe less prone to being pulled out of an orthopaedic implant since themating features can abut against a lip of a bore formed in the implant.

Another advantage is the mating features abutting against the lip of thebore allow the orthopaedic screw to apply a significant amount oftension to the orthopaedic implant using a mechanism other thancorresponding threads.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a perspective view of an embodiment of an orthopaedic implantaccording to the present invention;

FIG. 2 is a partially exploded view of another embodiment of anorthopaedic implant according to the present invention;

FIG. 3 is a cross-sectional view of a tibia with an orthopaedic implantfixated according to the present invention;

FIG. 4 is a cross-sectional view of a bone screw according to thepresent invention;

FIG. 5 is a cross-sectional partially exploded view of a tibia with anorthopaedic implant fixated according to the present invention;

FIG. 6 is an exploded view of a jig being used to prepare a tibiaaccording to the present invention;

FIG. 7 is an exploded view of a tibia with another embodiment of anorthopaedic implant fixated according to the present invention;

FIG. 8 is a cross-sectional view of the tibia with the orthopaedicdevice fixated shown in FIG. 7;

FIG. 9 is another perspective view of the tibia with the orthopaedicdevice fixated shown in FIG. 7;

FIG. 10 is an exploded view of a tibia with yet another embodiment of anorthopaedic implant fixated according to the present invention;

FIG. 11 is a cross-sectional view of a tibia with yet another embodimentof an orthopaedic implant fixated according to the present invention;

FIG. 12 is a cross-sectional view of the embodiment of the presentinvention shown in FIG. 11 having perpendicular protrusions rather thanangled protrusions;

FIG. 13 is a perspective view of an embodiment of yet anotherorthopaedic implant according to the present invention;

FIG. 14 is another perspective view of the embodiment of the presentinvention shown in FIG. 13;

FIG. 15 is a perspective view of a tibia with yet another embodiment ofan orthopaedic implant fixated according to the present invention;

FIG. 16 is a cross-sectional view of the embodiment of the presentinvention shown in FIG. 15;

FIG. 17 is an exploded view of a femur with an orthopaedic implantfixated according to the present invention;

FIG. 18 is a cross-sectional view of the embodiment of the presentinvention shown in FIG. 17;

FIG. 19 is yet another embodiment of an orthopaedic implant according tothe present invention;

FIG. 20 is a cross-sectional view of a femur with the orthopaedicimplant shown in FIG. 19 fixated according to the present invention;

FIG. 21 is yet another embodiment of an orthopaedic implant according tothe present invention;

FIG. 22 is a cross-sectional view of a femur with the orthopaedicimplant shown in FIG. 21 fixated according to the present invention;

FIG. 23 is an exploded view of a support body and bone ingrowth layeraccording to the present invention;

FIG. 24 is a partially exploded view of yet another embodiment of anorthopaedic implant incorporating the support body and bone ingrowthlayer shown in FIG. 23 according to the present invention;

FIG. 25 is a perspective view of yet another embodiment of anorthopaedic implant incorporating the support body and bone ingrowthlayer shown in FIG. 23 according to the present invention;

FIG. 26 is a perspective view of a tibia with the orthopaedic implantshown in FIG. 25 fixated according to the present invention;

FIG. 27 is a perspective view of a tibia with yet another embodiment ofan orthopaedic implant fixated according to the present invention; and

FIG. 28 is a perspective view of a tibia with yet another embodiment ofan orthopaedic implant fixated according to the present invention.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIGS. 1 and 2,there is shown an orthopaedic implant 30 which generally includes anarticulating tray 32, a support tray 34 connected to the articulatingtray 32, and a bone ingrowth layer 36 connected to the support tray 34.The articulating tray 32 has an articulating surface 38 that is shapedto be contacted by either a femur or tibia when the implant 30 is placedwithin a patient. The articulating surface 38 can be shaped to have aconcave portion 40 where a head of a femur or tibia will make contactwith the articulating surface 38 during implantation. The concaveportion 40 allows the head to glide smoothly across the articulatingsurface 38 during movement of the femur and tibia. An interface surface42 (shown in FIG. 2) is a surface of the articulating tray 32 that isopposite the articulating surface 38. The interface surface 42 can be aflat surface or can have features (not shown) formed on the surface 42that allow the articulating tray 32 to removably connect to the supporttray 34. FIG. 1 shows the articulating tray 32 being irreversiblyattached to the support tray 34 while FIG. 2 shows the articulating tray32 being reversibly attachable to the support tray 34. If thearticulating tray 32 is irreversibly attached to the support tray 34, apolymer retention layer 44 can be attached to the interface surface 42and support tray 34 to promote a better attachment of the articulatingtray 32 to the support tray 34. The articulating tray 32 can be madefrom any material suitable for providing an articulating surface 38 thatsimulates a patient's natural cartilage. A widely used material for suchan application is ultra-high molecular weight polyethylene (UHMW-PE),but other biocompatible polymers and metals could also be used.

A support tray 34 is connected to the interface surface 42 of thearticulating tray 32 and has a first connecting surface 46 that connectsto the interface surface, and a second connecting surface (not seen)that is opposed to the first connecting surface 46. The support tray 34is configured to be a complementary shape to the articulating tray 32 toprovide good attachment between the two components. The support tray 34provides additional rigidity and support to the articulating tray 32,which is typically thinner and made of lower strength material(s) thanthe support tray 34. As previously described, the first connectingsurface 46 can either attach directly to the interface surface 42, or beattached to the polymer retention layer 44 which will connect the firstconnecting surface 46 to the interface surface 42, especially in thecase that irreversible attachment is desired. As shown in FIG. 2, thefirst connecting surface 46 can be formed as a recess within the supporttray 34 to allow the articulating tray 32 to snap in to the recess andattach to the support tray 34. The support tray 34 lends strength to thearticulating tray 32, and can be made of any appropriate material(s) forthis purpose including titanium, stainless steel, cobalt chrome,hardened polymers and ceramics.

A bone ingrowth layer 36 is connected to the second connecting surfaceof the support tray 34. The bone ingrowth layer 36 can be shaped toentirely cover the second connecting surface of the support tray 34 oronly a portion of the surface. The bone ingrowth layer 36 allows forbone to grow into the layer 36, providing fixation for the implant 30 onthe femur or tibia. The bone ingrowth layer 36 is shaped to becomplementary to a prepared section of the femur or tibia where theimplant 30 will be fixated. The bone ingrowth layer is porous and canhave a roughened outer surface 48, which will provide immediate fixationto the prepared section through frictional forces caused by theabrasiveness of the roughened outer surface 48. Pores 50 can be formedthroughout the bone ingrowth layer 36 to allow for bone tissue ingrowthinto the layer 36. The pores 50 should be sized, shaped and distributedthroughout the layer 36 to allow for the desired amount of bone tissueingrowth, which will provide the fixation necessary for the implant 30to stay attached to the femur or tibia in the absence of bone cement orother attachment features. The pores 50 can also have biologicallyactive substances, such as growth factors, placed within to encouragebone tissue growth into the pores 50. Other biologically activesubstances that can be included in the pores 50 includeanti-inflammatories, antibiotics, painkillers, anti-rejection drugs andother medically useful substances. The bone ingrowth layer 36 can beformed from a variety of materials. Materials that have been found to beparticularly useful for forming the bone ingrowth layer 36 includetitanium, cobalt-chrome, stainless steel, polyether ether ketone (PEEK)and hydroxyapatite.

Referring now to FIG. 3, a cross-sectional view of the implant 30previously described is shown implanted in a tibia 52. Protrusions 54,56 are formed in the implant 30 and rest inside bores 58, 60 formed inthe tibia 52. Although the implant 30 is shown with the bone ingrowthlayer 36 attached, it is also contemplated that the bone ingrowth layer36 can be removed if the implant 30 has the protrusions 54, 56 included.The protrusions 54, 56 are angled relative to the support tray 34 andcan provide some fixation for the implant 30 while resting inside thebores 58, 60 before bone tissue ingrowth has begun in the bone ingrowthlayer 36. While protrusion 56 is shown as solid, protrusion 54 has abore 62 formed within having a pair of lips 64, 66 defining an entrance68 of the bore 62. While two lips 64 and 66 are shown as defining theentrance 68 to the bore 62, it should be appreciated that the lips 64and 66 can be placed elsewhere inside the bore 62 and the bore 62 mayhave only one lip or more than two lips. The bore 62 allows for atensioning member 70, shown as a compression screw, to be connected tothe implant 30, forming an orthopaedic implant system 71, and provide atensile force to the protrusion 54 that will bias the implant 30 towardthe tibia 52. Mating features 72 on the screw 70 abut against the lips64, 66 to keep the screw 70 connected to the protrusion 54. The matingfeatures 72 can be advanced partially or fully into the bore 62 toconnect the screw 70 to the implant 30 and interfere with the screw 70disconnecting from the implant 30, at which point the screw 70 can beadvanced away from the implant 30 to provide a controlled amount oftensile force to the protrusion 54 that biases the implant 30 toward thetibia 52 as the mating features 72 press against the lips 64 and 66. Themating features 72 can be formed without threads, i.e., be unthreaded.The protrusions 54 and 56 can be formed as an integral part of theimplant 30 or as an attachment to the implant 30. The protrusion 54 canbe formed of any materials capable of withstanding the tensile forceprovided to the protrusion 54, which will be similar to the materialsused to create the support layer 34.

FIG. 4 shows a cross-sectional view of the screw 70 shown in FIG. 3. Thescrew 70 has a main body 74 with outer threads 76 formed on a threadedportion thereof and the mating features 72 at one end of the main body74 and a torqueing end 78 at the other end of the main body 74. Thetorqueing end 78 can interact with a corresponding torqueing device toadvance the screw 70 into or out of the bore 62. The screw 70 has aninner chamber 80 formed within which has an inner threading 82 thatremovably mates with a support member 84, shown as an internal screw,within the inner chamber 80. As can be seen, the internal screw 84 hasan elongated support portion 86 connected to a main body 88 with a bore90 formed within to interact with a torqueing device and body threads 92formed on the surface to interface with the inner threading 82 of themain body 74 and removably couple the internal screw 84 to the main body74. When the screw 70 has the internal screw 84 sufficiently advancedwithin, the elongated support portion 86 is held within a separation gap94, shown as a split formed in the main body 74, between the matingfeatures 72 that extends into the inner chamber 80, preventing themating features 72 from advancing toward each other and maintaining theseparation gap 94 between the mating features 72. As can be appreciatedfrom FIGS. 3-4, when the support portion 86 is placed in the separationgap 94, the mating features 72 and support portion 86 define a supportedwidth W1 which is greater than a clearance width W2 defined between thelips 64 and 66. The supported width W1 being greater than the clearancewidth W2 interferes with the mating features 72 getting pulled out ofthe bore 62 and disconnecting the orthopaedic screw 70 from the implant30. While the support portion 86 is shown as substantially filling theseparation gap 94, i.e., filling at least 75% of the volume defined bythe separation gap 94, the support portion 86 can fill significantlyless of the separation gap 94 and still keep the mating features 72 fromadvancing toward each other and closing the separation gap 94.

Referring now to FIG. 5, the implant 30 with screw 70 inserted is shownwithout the internal screw 84 advanced within the inner chamber 80.Without the internal screw 84, there is nothing to keep the matingfeatures 72 separated so they can freely move toward each other. Thisallows the screw 70 to be advanced toward the bore 62 of the protrusion54 until the mating features 72 are pushed into the bore 62. Tapering ofthe mating features 72 allows the lips 64, 66 to push the matingfeatures 72 toward each other as the screw 70 is advanced into the bore62, closing the separation gap 94 between the mating features 72 andallowing the mating features 72 to snap out when the tapering advancesbeyond the lips 64, 66, providing an abutment of the mating features 72to the lips 64, 66. In this sense, the mating features 72 define amating width when the separation gap 94 is partially or fully closedthat is less than the clearance gap W2 of the lips 64 and 66 to allowthe mating features 72 to advance into the bore 62 when the matingfeatures 72 partially or fully close the separation gap 94 but alsoforming the abutment when the separation gap 94 is fully open. Thisabutment allows for tension to be transmitted to the protrusion 54 asthe screw 70 is advanced away from the implant 30. Once the abutment isformed, the internal screw 84 is advanced in the inner chamber 80 sothat the elongated support portion 86 travels through the inner chamber80 to occupy the separation gap 94 between the mating features 72,preventing the mating features 72 from advancing toward each other asthe screw 70 is advanced away from the implant 30 and maintaining thesupported width W1. To limit advancement of the internal screw 84 withinthe inner chamber 80, the main body 88 of the internal screw 84 can havea body width W3 which is approximately equal to an internal width of theinner chamber 80 while the support portion 86 has a support width W4which is less than the body and internal width W3. As can beappreciated, the previously described mating width of the matingfeatures 72 is equal to the supported width W1 minus the support widthW4. The body and internal width W3 being greater than the support widthW4 prevents the main body 88 of the internal screw 84 from advancinginto the separation gap 94, which can have a width approximately equalto the support width W4, while allowing the support portion 86 to beadvanced into the separation gap 94 as the internal screw 84 advances inthe inner chamber 80. Once it is desired to remove the screw 70 from theimplant 30, the internal screw 84 can be advanced out of the screw 70and the screw 70 can then be advanced out of the bore 62.

Referring now to FIG. 6, a jig 96 is shown that can be used to formbores 58 and 60 seen in FIG. 3 into the tibia. The jig 96 has multipleanchoring openings 98 through which pins 100 can be inserted to attachthe jig 96 to a prepared surface 102 of the tibia. The jig 96 has drillopenings 104 that are angled and positioned to correspond to where theprotrusions 54 and 56 will be when the implant 30 is placed in theprepared surface 102. Once the jig 96 is placed, bores 58 and 60 can beformed by advancing a drill (not shown) through the drill openings 104.

The main body 74 includes a terminal end 79 opposite the torqueing end78. At least one of the mating features 72, shown as both matingfeatures 72 in FIG. 4, has a first tapered portion 81 with an increasingwidth relative to the terminal end 79 and a second tapered portion 83. Anon-tapered portion 85, with a constant width, is between and connectsthe first tapered portion 81 and the second tapered portion 83, whichhas a decreasing width relative to the non-tapered portion 85. The mainbody 74 defines a longitudinal axis LA that extends through thetorqueing end 78 and the terminal end 79 of the main body 74. In someembodiments, the two mating features 72 each have a respectivenon-tapered portion 85, with the non-tapered portions 85 being alignedradially, relative to the longitudinal axis LA, with one another. Insome embodiments, the main body 74 also includes an additionalnon-tapered portion 87 between the threaded portion of the main body 74with threads 76 and the mating features 72.

Referring now to FIGS. 7, 8 and 9, an orthopaedic implant 110 is shownthat includes a main body 112, a first protrusion 114, an elongatedprotrusion 116 and a second protrusion (not shown). The main body 112can be similar to the previously described implant 30, shown herewithout the bone ingrowth layer 36 attached. The first protrusion 114and the second protrusion can be structured similarly to the protrusion54 previously described and shown, to interact with a screw 118 andinternal screw 120 that are structured similarly to the screw 72 andinternal screw 84 previously described and shown. The elongatedprotrusion 116 fits into a bore formed in a tibia 122 to help balancethe tension that is applied to the first protrusion 114 and secondprotrusion. As shown in FIG. 9, when the implant 110 is fully installed,there will be a pair of screws 118 holding the implant 110 tensioned tothe tibia 122. It is also contemplated that an implant could be fixatedto the tibia 122 using only one protrusion 114 and screw 118.

FIG. 10 shows an orthopaedic implant 130 that is similar to theorthopaedic implant 110 previously described, but lacking the elongatedprotrusion 116. The implant 130 has a pair of protrusions 132, 134 thatcan receive a tensile force from screws 136, 138. The screws 136, 138can be structured similarly to previously described screws 70 and 118with internal screws 84 and 120.

Referring now to FIGS. 11 and 12, an orthopaedic implant 140 is shownthat includes an articulating tray 142, a support tray 144 connected tothe articulating tray 142, and a bone ingrowth layer 146 connected tothe support tray 144. The implant 140 can be configured in similarfashion to the implant 30 described and shown previously. The implant140 also has a protrusion 148 formed as part of the support tray 144 anda protrusion 150 formed as part of the bone ingrowth layer 146. Theprotrusions 148 and 150 can be angled relative to a bottom surface 152of the articulating tray 142, as shown in FIG. 11, or be perpendicularto the bottom surface of articulating tray 142, as shown in FIG. 12. Theprotrusion 148 has an opening 154 formed through that allows theprotrusion 148 to connect to a tensioning member 156. The tensioningmember 156 includes an anchor 158, shown as a button with a largerdiameter than protrusion 148, and a tension transmitter 160, shown as asuture. The button 158 has multiple openings 162 for the suture 160 topass through. To fixate the implant 140, a pair of bores 164, 166 thatclosely match the size of protrusions 148 and 150 are formed in a tibia168 and protrusions 148 and 150 are placed in the bores 164, 166. Thesuture 160 is then passed through one of the openings 162 on the button158, advanced through the bore 164 where protrusion 148 rests, passedthrough the opening 154 on protrusion 148, advanced out of the bore 164and passed through another opening 162 on the button 158 to form a loopof suture. This process can be repeated as many times as desired toproduce one or more loops of suture. When the desired number of loopsare formed, the suture 160 can be pulled to provide a tensile force tothe protrusion 148, forcing the implant 140 into the tibia 168, and thentied to maintain the tensile force on the protrusion 148. The tensileforce from the suture 160 tied to the protrusion 148 helps fixate theimplant 140 to the tibia 168 while bone tissue grows into the boneingrowth layer 146. If desired, bone cement could be used rather thanthe bone ingrowth layer 146 to help fixate the implant 140 to the tibia166. The tensioning member 156 could also be changed to accommodatedifferent surgical techniques.

Referring now to FIGS. 13 and 14, an orthopaedic implant 170 is shownthat includes an articulating tray 172, a support tray 174 connected tothe articulating tray 172, and a bone ingrowth layer 176 connected tothe support tray 174. The articulating tray 172 and support tray 174 ofimplant 170 can be configured similarly to the previously describedarticulating tray 32 and support tray 34 of orthopaedic implant 30. Thebone ingrowth layer 176 includes multiple protrusions 178 integrallyformed in the bone ingrowth layer 178. These protrusions 178 can beshaped as cylindrical pegs to fit in bores formed on a tibia. A fixationplate 180 is connected to the support tray 174 and includes multipleopenings 182. The openings 182 are sized to have screws passed through,that will help fixate the implant 170 to the tibia during implantation.The implant 170 will typically be an onset unit, where the tibia isprepared by creating a flat surface on the tibia where the implant 170rests.

FIGS. 15 and 16 show an orthopaedic implant 190 similar to theorthopaedic implant 140 previously described, but having an articulatingtray 192, support tray 194 and bone ingrowth layer 196 that are shapedto make the implant 190 an inset implant that rests within a tibia 198.The articulating tray 192 has a pair of tapered surfaces 200 thatconform to a surface 202 of the tibia 198, allowing for as much of thetibia 198 to be preserved as possible while still attaining a goodfixation of the implant 190. The support tray 194 has a protrusion 204with an opening 206 and the bone ingrowth layer 196 has a protrusion 208similar to previously described orthopaedic implant 140. The tensioningmember 156 could be used to apply tension to protrusion 204, aspreviously described. Fixating the implant 190 would be accomplished ina similar fashion to the way orthopaedic implant 140 is fixated.

While the previously described implants and fixation techniques have allbeen described for use in a patient's tibia, similar implants andtechniques can be used for implant fixation in a patient's femur.

As shown in FIGS. 17 and 18, an orthopaedic implant 210 can be fixatedin a patient's femur 212 in a similar fashion to the previouslydescribed implants for a patient's tibia. The implant 210 has a curvedarticulating tray 214 and a curved body tray 216 connected to thearticulating tray 214. The articulating tray 214 and body tray 216 arecurved to conform to the anatomical shape of the femur 212. The bodytray 216 has a pair of protrusions 218 integrally formed that are placedin a pair of bores 220 formed in the femur 212. The protrusions 218 canbe structured any way previously described for use in a tibia. A pair ofscrews 222, similar to previously described screws with internal screws,are inserted into the protrusions 218 and, once they are locked into theprotrusions 218, advanced out of the bores 220 to provide a tensileforce fixating the implant 210 to the femur 212. While implant 210 isnot shown with a bone ingrowth layer attached to the body tray 216, sucha layer could be attached to the body tray 216 to provide extra fixationto the implant 210.

Referring now to FIGS. 19 and 20, an orthopaedic implant 230 is shownthat can be fixated in a patient's femur 232. The orthopaedic implant230 includes a curved body tray 234 with an articulating surface 236 anda bone ingrowth layer 238 attached to the body tray 234 at a surfaceopposite the articulating surface 236. The body tray 234 andarticulating surface 236 can be structured as previously described. Apair of pegs 240 are bonded to the bone ingrowth layer 238 andconfigured similarly to previously described protrusion 54. The pegs 240each have a bore 242 with an entrance 244 formed within and lips 246near the entrance 244. The lips 246 allow screws 248, similar topreviously described screws with internal screws, to lock into the pegs240 and apply a tensile force to the pegs 240, similar to previouslydescribed screws. The pegs 240 can be made of titanium and bonded to theimplant 230 by any means that allow for a secure bond.

Referring now to FIGS. 21 and 22, an orthopaedic implant 250 is shownthat includes a body tray 252 with an attached bone ingrowth layer 254.The bone ingrowth layer 254 is bonded to a pair of split pegs 256. Thesplit pegs 256 each have an end 258 bonded to the bone ingrowth layer254 and a pair of outside lips 260 at an opposite end 262. The outsidelips 260 are tapered so that they have a lowest diameter d1 at end 262that increases to a max diameter d2 in the direction of end 258. A split264 in the pegs 256 allows the outside lips 260 to be pushed toward eachother when the pegs 256 are advanced in a pair of bores 266 formed in afemur 268. The bores 266 have a first length L1 with a diameter D1,which is close to diameter d1, and a second length L2 with a largerdiameter D2. As the pegs 256 advance through the first length L1 of thebores 266, the outside lips 260 are pushed toward each other to give thepegs 256 an overall diameter less than D1, allowing advancement of thepegs 256 through the bores 266. When the pegs 256 advance such that themax diameters d2 of the lips 260 reach the second length L2, the lips260 expand away from each other to give the pegs 256 an overall diameterclose to the max diameter d2. When this occurs, the pegs 256 cannoteasily be pulled away from the femur 268 as the lips 260 will abutagainst the femur 268 in the bores 266 at the intersection of the firstlength L1 and the second length L2. The pegs 256 can be made from anymaterial giving suitable strength for such an application, includingPEEK, titanium, cobalt chrome, resorbable materials or other polymermaterials.

In certain applications, it may be useful to provide an orthopaedicimplant of the present invention with a way to deliver drugs and othertherapeutic agents to surrounding anatomy structures. FIG. 23 shows asupport body 270 connected to a bone ingrowth layer 272 that is modifiedto deliver drugs to surrounding anatomy structures. The support body 270is formed from a first side 274 having an inner surface 276 and an outersurface 278 (shown in FIG. 24) and a second side 280 having an innersurface 282 and an outer surface (not shown) that attaches to the boneingrowth layer 272. Both inner surfaces 276, 282 have channels 284, 286formed within that combine to form a reservoir within the support body270 when the first side 274 and second side 280 are connected. Elutionopenings 288 are formed in the channels 286 of the second side 280, andgo through the support body 270 to the bone ingrowth layer 272. Theseelution openings 288 allow drugs and therapeutic agents from thereservoir to flow into the porous bone ingrowth layer 272 and out tosurrounding anatomy structures. Each side 274, 280 can have a portchannel 290 that extends through the support body 270 to form a port 292(shown in FIG. 24) that allows for refilling the reservoir. FIGS. 24 and25 show an orthopaedic implant 294 incorporating the support body 270that is modified for drug delivery. As can be seen, the outer surface278 of the first side 274 has a recess 296 formed therein to allow for areversible connection of an articulating tray 298. The outer surface 278can also be configured to irreversibly connect to the articulating tray298. When the reservoir of the support body 270 is full, a stopper 300can be inserted in the port 292 to prevent drugs or therapeutic agentsfrom leaking out of the reservoir. FIG. 26 shows the orthopaedic implant294 fixated on a tibia 302 according to embodiments of the presentinvention, but the orthopaedic implant 294 could also be fixated on afemur according to embodiments of the present invention. FIG. 27 showsthe orthopaedic implant 294 with a refill interface 304, rather than thestopper 300, inserted in the port 292. The refill interface 304 can be acircular disc 306 placed inside or outside of a patient with an opening308 connected to a tube 310 that goes into the reservoir to provide away to refill the reservoir with drugs or therapeutic agents. A one-wayvalve can be placed in the opening 308 to prevent drugs or therapeuticagents from coming out of the opening 308. Drugs and therapeutic agentscan be injected into the port 292 or refill interface 304 using asyringe or other similar tool. FIG. 28 shows an alternative refillinterface 320 which is a therapeutic reservoir 322 with a tube 324 goingthrough the port 292 and into the reservoir of the support body 270. Thetherapeutic reservoir 322 can be shaped and placed either within oroutside of a patient. One useful placement of the therapeutic reservoir322 might be near a patient's knee, such that when the patient takes astep, forces from anatomy structures around the reservoir 322 wouldsqueeze the reservoir 322, designed as a bag, and force drug into thereservoir of the support body 270 which would then be forced into thebone ingrowth layer 272.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

What is claimed is:
 1. An orthopaedic screw, comprising: a main bodyhaving a torqueing end, a terminal end opposite the torqueing end, aninner chamber formed therein, and at least two mating features separatedby a separation gap, said separation gap extending into said innerchamber, at least one of said at least two mating features having afirst tapered portion with an increasing width relative to the terminalend, a second tapered portion, and a non-tapered portion between andconnecting the first tapered portion and the second tapered portion, thesecond tapered portion having a decreasing width relative to thenon-tapered portion, the second tapered portion defining an acute anglerelative to a longitudinal axis of the main body, the at least one ofsaid at least two mating features being unthreaded; and a support memberremovably placed in said inner chamber of said main body and having asupport portion at least partially filling said separation gap betweensaid at least two mating features.
 2. The orthopaedic screw according toclaim 1, wherein said separation gap is a split formed in said mainbody.
 3. The orthopaedic screw according to claim 1, wherein saidsupport portion interferes with said at least two mating featuresadvancing toward each other.
 4. The orthopaedic screw according to claim1, wherein said support portion substantially fills said separation gap.5. The orthopaedic screw according to claim 1, wherein said internalchamber has a threading formed therein and said support member is aninternal screw having a screw body with a body threading formed thereon,said body threading of said screw body interfacing with said threadingof said internal chamber to removably couple said support member to saidmain body.
 6. The orthopaedic screw according to claim 1, wherein saidinternal chamber defines an internal width and said support portiondefines a support width which is less than said internal width.
 7. Theorthopaedic screw according to claim 1, wherein said at least two matingfeatures are unthreaded.
 8. The orthopaedic screw according to claim 7,wherein said main body includes a threaded portion having a plurality ofthreads and an additional non-tapered portion between said threadedportion and said at least two mating features.
 9. An orthopaedic screw,comprising: a main body having a torqueing end, a terminal end oppositethe torqueing end, an inner chamber formed therein, and at least twomating features separated by a separation gap, said separation gapextending into said inner chamber, at least one of said at least twomating features having a first tapered portion with an increasing widthrelative to the terminal end, a second tapered portion, and anon-tapered portion between and connecting the first tapered portion andthe second tapered portion, the second tapered portion having adecreasing width relative to the non-tapered portion, the second taperedportion defining an acute angle relative to a longitudinal axis of themain body, the at least one of said at least two mating features beingunthreaded.
 10. The orthopaedic screw according to claim 9, wherein saidseparation gap is a split formed in said main body.
 11. The orthopaedicscrew according to claim 9, wherein said at least two mating featuresare unthreaded.
 12. The orthopaedic screw according to claim 11, whereinsaid main body includes a threaded portion having a plurality of threadsand an additional non-tapered portion between said threaded portion andsaid at least two mating features.
 13. An orthopaedic screw, comprising:a main body having a torqueing end, a terminal end opposite thetorqueing end, an inner chamber formed therein, and at least two matingfeatures separated by a separation gap, said separation gap extendinginto said inner chamber, said at least two mating features including afirst mating feature having a first tapered portion with an increasingwidth relative to the terminal end, a second tapered portion, and anon-tapered portion between and connecting the first tapered portion andthe second tapered portion, the second tapered portion having adecreasing width relative to the non-tapered portion, the second taperedportion defining an acute angle relative to a longitudinal axis of themain body, the at least two mating features being configured to movetowards one another and then snap out following advancing of the atleast two mating features past lips of a bore.
 14. The orthopaedic screwof claim 13, wherein the main body defines a longitudinal axis extendingthrough the torqueing end and the terminal end, the at least two matingfeatures including a second mating feature having a respectivenon-tapered portion that is aligned radially, relative to thelongitudinal axis, with the non-tapered portion of the first matingfeature.